The invention relates to a process for correcting angle errors when establishing the driving direction of vehicles with an electronic compass. From DE-PS No. 27 54 888 it is known to establish the driving location of a vehicle in a navigation apparatus with a biaxial magnetometer, whose output signals for the compensation of magnetic interference fields in the vehicle are fed to a correction unit wherein a zero point displacement of the output signals as well as a proportional change of one of the output signals is performed. With this solution one assumes that an interference field with a defined vector is present in the vehicle which is superimposed by the earth's magnetic field which is more or less screened by the automobile body depending on the alignment of the vehicle. Since the earth's magnetic field, which is decisive for the driving direction, engages the earth's surface obliquely from above under the so-called inclination angle with respect to the horizontal, only the component is picked up by the magnetometer which is in the plane of driving during the establishment of the drive direction. One axis of the magnetometer is provided in the driving direction and the other transversely to the driving direction. In the stationary installed electronic compass, no measuring error occurs as long as the vehicle drives in a horizontal direction. However, during ascent or descent, an angle error is generated in the electronic compass during the measuring of the driving direction, which may be up to 30.degree. depending on the ascent or descent and dependent on the driving direction. If this angle error is to be avoided, the magnetometer must be provided with a cardanic suspension which is expensive and susceptible to interference, so that the axes of the magnetometer are also in one horizontal plane during ascent and descent driving. However, measuring errors are generated when driving through curves, during acceleration or braking of the vehicle.
It is therefore desireable to compensate the angle errors, which depend from the incline of the vehicle in its longitudinal axis, in a very simple manner.